It is known in the art to make shaped metal cans consisting of a peripheral wall having at least one expanded region, a bottom crimped or seamed onto one end of the peripheral wall and a lid crimped or seamed onto the other end of said peripheral wall. The lid is provided for example with a device which is easily opened by rupture of a line of reduced strength or for example with a tapped neck for receiving a screwed stopper. The peripheral wall of this type of metal can is generally constituted by a cylindrical sleeve welded longitudinally and including at least one expanded region. Usually the peripheral wall is made from a metal blank of soft steel having a low carbon content and a yield strength of about 250 MPa.
Soft steel of this type permits effecting, without great difficulty, a local expansion of the welded cylindrical sleeve with an expansion ratio calculated from the formula ##EQU1## which may be as much as 20%, "initial D" being the initial diameter of the welded sleeve and "final D" being the diameter of the welded peripheral wall after expansion.
To manufacture this type of shaped can, the welded sleeve is produced and expanded locally to form a peripheral wall or skirt comprising at least one expanded region, and the bottom and lid are respectively crimped or seamed onto each end of the peripheral wall.
The expanded region is usually formed by effecting an overall expansion on the whole of the height of the region to be expanded, by a forming process employing air or nitrogen under pressure or by a forming process employing an incompressible fluid or by a mechanical expansion process employing a tool having sectors.
It is also known to make shaped metal cans consisting of, on one hand, a bottom and a peripheral wall in one piece with said bottom and, on the other hand, a lid crimped or seamed onto the peripheral wall. The bottom and the peripheral wall in one piece (integral) with the bottom are made from a cup cut from a metal blank or strip, e.g., either by drawing and redrawing or by drawing and ironing. However, when making this type of can with the drawing and redrawing technique, after the forming of the peripheral wall, the metal is in a highly work-hardened state so that the yield strength of said peripheral wall is about 600 MPa. The possible overall expansion ratio of such a peripheral wall is only about 2.5%. When making this type of can by the drawing and ironing technique, after the drawing of the peripheral wall, the metal is in an even more highly work-hardened state so that the yield strength of the peripheral wall is about 700 MPa and sometimes even more, which imparts to this wall a substantially zero expansion capability. The possible overall expansion ratio of such a peripheral wall is lower than 1% and for very small thicknesses lower than 0.5%. Such low expansion ratios are generally unacceptable and preclude substantial can volume increases and wall thinning.
On the other hand, the advantage of a metal can produced by the drawing and redrawing technique or by the drawing and ironing technique is that it permits very small thicknesses since the metal of the can is very stiff with very high mechanical characteristics, which results in light weight and a low expenditure of material. Further, such a can is made in two parts, the bottom and the peripheral wall being in one piece, which is an advantage from an aesthetic point of view.